Home | About | Sematext search-lucene.com search-hadoop.com
 Search Hadoop and all its subprojects:

Switch to Threaded View
MapReduce, mail # user - Some general questions about DBInputFormat


Copy link to this message
-
Some general questions about DBInputFormat
Yaron Gonen 2012-09-11, 12:41
Hi,
After reviewing the class's (not very complicated) code, I have some
questions I hope someone can answer:

   - (more general question) Are there many use-cases for using
   DBInputFormat? Do most Hadoop jobs take their input from files or DBs?
   - What happens when the database is updated during mappers' data
   retrieval phase? is there a way to lock the database before the data
   retrieval phase and release it afterwords?
   - Since all mappers open a connection to the same DBS, one cannot use
   hundreds of mapper. Is there a solution to this problem?

Thanks,
Yaron